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IMPROVED METHOD OF FEEDING SLURRY FORM CATALYSTS TO A GAS PHASE REACTOR

IP.com Disclosure Number: IPCOM000021574D
Publication Date: 2004-Jan-23
Document File: 6 page(s) / 46K

Publishing Venue

The IP.com Prior Art Database

Abstract

Improved Method of Feeding Slurry Catalysts to a Gas Phase Reactor A method of controlling the size of drops of liquid catalyst entering a gas phase polymerization reactor is taught herein to prevent the formation of large flaky particles which might result from the use poorly distributed polymerization catalysts suspended in a slurry, particularly mineral oil slurry. Said control is affected by using a either perpendicular spray nozzle or a perpendicular effervescent nozzle which produce finer catalyst slurry droplet dispersions, resulting in smaller individual droplets of contained catalyst and slurry solvent which results in fewer agglomerates and better overall catalyst utilization.

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Improved Method of Feeding Slurry Form Catalysts

to a Gas Phase Reactor

Slurry catalysts are well known and are particularly suitable for use in olefin polymerization in the gas phase. Particular problems, however, can result from use of slurry catalysts that are present in heavy diluent such as mineral oils. With improper design of the injection method into the reactor, it is possible to get catalyst that "drools" into the reactor forming catalyst balls or clumps resulting in poor reactor operation and poor catalyst efficiency. Even with proper design (using Nitrogen gas to blow material into the reactor or solvent to blow/disperse the catalyst into the reactor) at low feed rates catalyst maldistribution is still possible, resulting in poor overall system performance. Higher nitrogen gas feed or solvent feed can improve this situation but can result in a build-up of inerts in the system that is detrimental to performance. Improved dispersion is particularly important for catalyst systems with very low (essentially immediate initiation) induction time.

A method of controlling the size of drops of liquid catalyst slurry entering a gas phase polymerization reactor is taught herein to prevent the formation of large flaky particles which might result from the use poorly distributed polymerization catalysts suspended in a slurry, particularly mineral oil slurry. Said control is affected by using a either perpendicular spray nozzle or a perpendicular effervescent nozzle which produce finer catalyst slurry droplet dispersions, resulting in smaller individual droplets of contained catalyst and slurry solvent which results in fewer agglomerates and better overall catalyst utilization.

BACKGROUND OF THE INVENTION

Slurry polymerization catalysts are widely used in the production of polyolefins. Typically, the catalyst will be injected into a gas phase polymerization reactor (most often as a slurry in a high viscosity media which prevents slurry settling). The catalyst slurry is then typically dispersed in the reactor by action of a nitrogen (or other inert gas) carrier stream or by dispersion in a solvent (such as hexane, isopentane or the like). In certain cases, particularly where catalyst initiation is rapid, even this level of dispersion is ineffective in preventing formation of agglomerates. This process can also be used in what is considered to be a "particle lean zone" which can be created by feeding a jet of heated monomer or cycle gas into the side of the reactor. This is particularly useful in cases in which extraordinarily rapid initiation occurs. It allows a brief period of time for the spray droplets to begin polymerization before contacting the polymer particles already in the reactor, thus reducing the tendency for the catalyst slurry droplets to adhere to the already formed particles.

Even with use of a particle lean zone, inefficient catalyst dispersion can commonly yield particle agglomerates that restrict reactor operability. These pa...